Thermostatic draft control



March 24, 1942.

c. B. HARRELL T HERMOSTATIC DRAFT CONTROL Filed July 22, 1940 2Sheets-Sheet 1- f -i tt l- L, If

March 24, 1942. c, B, HARRELL THERMOSTATIG DRAFT CONTROL 2 Sheets-Sheet2 Filed July 22, 1940 6 ,5. Ha rreZZ Patente 24, E942- para o earners Igusts fer as "at 2 Clas.

The invention relates to means for controlling the draft to spaceheaters, and particularly to the control of the draft in stoves forheating liv'- ing rooms and the like, or other places, and which will beresponsive in'a novel wayto the require- 5 ments of a given space forheat, in order to maintain it' at or near a predetermined temperature,as distinct from devices that operate in response to the temperaturewithin the heater itself to control a damper orvthe like, as asafetyappliance or to maintain the unit at a predetermined heatproduction condition.

An important aim of the invention is to present an improvement inconstruction of such devices,

to the end that the functioning of the device will be more dependablefor controlling room temperatures, and which will enable the productionof the article so as to occupy an extremely small place in aninconspicuous and safe position, where it will be liable in a minimumdegree to damage or derangement by being struck by articles, implementsor particles of fuel, as well as obviating the need for projecting partswhich might represent liability of accidental operation of the device,or engagement in clothing or objects, with resultant damage orimpairment of function of the device.

It is also an aim of the invention to presen such construction in whicha very simple control and regulating means may be provided of the 3:)

most extreme simplicity, whereby any ordinary person may be able toadjust the device to secure its best function. Another important aim ofthe invention is to present a construction which will be extremelysimple, so-that its parts may be 5 materials and at a low cost forproduction and 40 assembly.

A further important aim of the invention is to present such an articlewhich is adapted, without material change, to use upon various types ofstoves, furnaces, and other equipment and heaters, adaptable towood-burning stoves, coal stoves, and burners of other fuel, as willappear hereinafter.

It is a further advantage of the invention that it will respond'tocooling of rooms'incident to ventilation, and generally operate as apart of a room unit, as distinct from ,a mere burner or combustiondevice. It is an important aim of the invention to present a novel meansfor controlling or regulating and changing the function (or, gre se) ofthe device in operating a damper or draft shutter, so that the automaticfunction of the device may be definitely established at will, withp inany desired range of operation in relation to an arbitrary roomtemperature desired by the operator.

Additional objects, advantages and features of invention reside in thearrangement, construction and combination of parts involved in theembodiment of the invention, as will be more readily understood from thefollowing description and accompanying drawings, wherein Figure 1 is afront view of a simple wood-burning stove, in which the invention isincorporated, although the invention is also applicable to coal burningand other forms of stoves and furnaces, as well as being adapted tocontrol liquid fuel valves andbther elements, these variations not beingillustrated, since they will be readily understood and apparent from thepresent disclosure and knowledge of construction of various types ofheaters in the art.

Figure 2 is a side elevation of the stove shown in Figure 1;

Figure 3 is a fragmentary cross section on .the

line 33 of Figurez. 4

Figure 4 is a vertical longitudinal sectional view of the draft fluetaken in the major plane Figure 8 is an'elevatio'n at right angles toFigure 7.-

There is illustrated in Figures 1 and 2 a com-- mon form of wood-burningstove, often called King Heaters," having a stoking door H in the 4 topthereof, and a smoke pipe l2 leading out of the 'top at the rear, whileat the forward end of the stove means for admitting air by a ,downdraftflue i3 is provided, the flue i3 opening into the lower part of thecombustion chamber of the stove by means of a. usual fitting Hl'securedto the front end of the stove, and upon which the flue I3 is erected,the latter being formed of common rolled iron sheeting, after the commonpractice in the production of stove-pipe. In the present instance theflue I3 is enlarged gradually toward its upper end, where it is ofcircular form,

closed by a manually operable draft shutterl5 of any usual constructionby which an arbitrary limitation of draft through the tube may be ef#fected', as required, or, the draft may be entirely cut off thereby,these functions being well understood in such appliances.

The flue I3 is located very close to the front of the stove at its lowerend, but is inclined outwardly therefrom at its upper part, affording aspace at l8, within which my automatic control device is mounted,'-sothat the flue It serves as a guard for the more or less delicatethermostat device,,its mounting, and connections between the same andthe draft shutter in the flue, as will be described.

Set across the flue it near its upper end there is a stationary,circular port plate l'l comprising three sector-shaped portions l8joined at the center by a small circular integral disc portion l9, andconnected at their 'outer parts by a continuous annular portion 20, theintervals between these sector portions constituting ports 2|coextensive with the sector portions l8 in the same annular zone. Theport plate generally is in the form of a segment of a sphere, thespherical portion extending into the rim 20 a distance, but stoppingshortof the outer edge or periphery of the rim 20, being bounded by anupwardly pressed portion of the plate, as at 22, extending entirelyaround the plate, the peripheral edge of the plate terminating in adownwardly turned approximately cylindrical flange 23. This plate ismade with a diameter which is slightly less than the interior diameterof the flue at its upper extremity, and is secured in place byv beingpressed into the flue end, which is tapered downwardly, until the metalof the flue is slightly expanded or pushed outwardly, this forming asufficiently perthe flue, although it may be welded or otherwise securedin accordance with familiar prac-' pressed portions of the flange, asindicated in notched to receive the ear therein, so that the shutter maylie in registration with the sectors and ports of the plate ll, when inopen position,

and so that the ports in the plate I! may be completely closed when theshutter is at the opposite limit of its movement. It will be noted fromFigure 3, that one of the sectors of the .,U'-shaped in cross section,the body web portion I manent attachment of theplate H in place inFigm'e 3, at24. A shutter is provided, correspending generally in formto that part of the plate I! whichlies inwardly of the upwardly pressedboundary wall 22 of the plate, having however, a rim portion 26 ofslightly less diameter than the inner surfaces of the boundary flange22, so that the shutter may be free to rotate within the flange 22without interfering or friction. This shutter is also in the form of asegment of a sphere, approximately, but preferably formed on a slightlylonger radius, so that while its center may rest upon the disc l9 at thecenter of the plate I], its outer edge portion will clear the plate I!so that the shutter may rotate freely thereon without requiring aspacer. It is pivoted upon the plate I! by means of a usual rivet 21 orother'pivot element, as may be found desirable. The shutter is formedwith three vanes 28, and corresponding ports 29 all of which areadaptedto register respectively with the sector parts and V portsof the-portplate IT, as may be seen. Set

rigidly in one of the vanes there is a wrist pin 29 or stud, upstandingfrom the vane. One of the vanes '28 has an ear extended from one edge,and bent downwardly so as to lie within one of the ports of the platevl1, serving as a stop to limit movement of the shutter in respectivedirections by engaging the edges of the ports. In the present instance,the edges of the ports through which the ear is projected may be beingsecured against the rear face of the flue l3 by welding or otherwise.foramin'ate as at 33, to permit free circulation of air laterallytherethrough, for a purpose to be made clear. A resilient bi-metallicbar or strip 34 is mounted at the lower end portion of the guard piece,and in practice, a strip approximately six inches in length has beenused, the upper end of which extends slightly above the shutter level,and the lower end is'secured fixedly in relation to the flue, andin'spaced relation to the guard piece 3| and the flue l3, by. anyapproved fastening, at 35. :In .the present instance, washers areinserted between the strip inner end of thebolt within the flue. Theupper end of the strip is the oscillating portion, and in the presentinstance, it is considered material to have that part of strip 34 withthe highest coefllcient of expansion presented toward the stove, thearrangement being such that direct radiation of heat from the surface ofthe stove will be incident upon the strip 34 without impeding materialother than air. The upper end of the strip is apertured, and haspivotally connected thereto a link 36, which in the present instance,may be formed of heavy wire stock with an eye portion engaged around thewrist pin 29. This link extends radially from the strip 34 inwardly,through a suitable aperture in the guard piece 3| and flue for adistance, and is then offset and extended in a parallel direction to theeye portion thereon, so that in inward slidingmovement of the link, itwill clear the pivot pin 21 of the shutter.

The bi-metallic strip 34 normally is curved away from the flue II at theupper end of the strip, and it will be seen that when heated, theexpansion of the outer element of higher coeflicient of expansion willcause the. upper end of the strip to move inward toward the flue,pushing the wristpin of the shutter. so as to rotate'the shutterclockwise and toward closed position, in a degree corresponding to theeffect of heat on the bi-metallic strip, and proportional to thetemperature at which the end of the strip is positioned by the heatacting thereon, counteracte i by the draft of air which will passupwardly beoutward again, drawing the shutter counter- Its flanges 32are earners clockwise and opening the ports of the plate ii, therebysupplying more oxygen to the stove, the fuel in which will burn withgreater intensity and tend to raise the temperature of the roomcorrespondingly.

In order to adjust the function of the damper to suit the requirementsof suchjindividuals or special climatic conditions, size of the room,and other factors, I have providedmeans for varying the function of thebi-metaliic strip. consists of a shaft 38, mounted revolubly across theflue it, extending from front to rear, the rear end extending alsothrough the web body of the channel-shaped guard piece at, slightly toone side of the bi-metallic strip 3 3, and having l5 fixed thereon aconcentric worm grooved cam 39, the periphery of this cam extendingbeyond the adjacent edge of the strip 35, a distance, so that the edgeportion of the strip sets in the worm groove of the cam, and wherebyrotation'go of the cam will press the engaged edge portion of the striprearwardly from the direction of the flue, or will allow it to moveforwardly toward its normal initial psition. The forward end of theshaft 38 is provided with a hand lever 40, the hub of which is formedwith a pointer 4i,

arranged in indicating relation to a dial or other indicia 42 formed ona semi-circularbearing fitting 43 attached to the front side of the flueexteriorly thereof. The cam groove is of such lead that movement of thelever til over an angle of '180 degrees will efiect the full range ofadjustment of the bi-metallic strip, and the indicia 42 is corelated tothe effect produced on the bimetallic strip by the cam, in its result inmoving as the shutter.

The device being installed as illustrated, it will be understood thatwith a fire maintained in the stove, the heat radiated to thethermostatic strip 36 will tend to cause the upper end thereof to moveforwardly toward the flue and operate the shutter to close the portsthrough the plate l1, and that, initially, when a fire is started, the

, cool thermostatic strip will hold the shutter in open position so thata maximum draft is afford- 45 fire when the temperature of the room hasrisen 5 sufiiciently to minimize'the counteracting effect of aircirculation opposed to the heating of the stripby radiation from thestove.

In Figure 5, the application of the invention to use upon a down-draftpipe for one type of 5 coal-stove, commonly used, as illustrated, inwhich a central flue $5 is mounted in the top of the stove and normallyopen at its upper end, but closed by a shutter operating upon a portplate of the same construction as the port plate and shutter previouslydescribed. The stove has a smoke pipe 46 leading upwardly therefrom atthe rear, and upon the side of this there issuitably fixed the face of abimetallic strip 41 extending forwardly beside the opening at the upperend of the flue, $5, and having a link connection 48 from its forwardextremity to the shutter, the strip being properly disposed and arrangedto effect closing of the shutter at high temperatures and openingthereof at low temperatures, as desired. The cam adjustment in thisinstance, for controlling action of the thermostatic strip comprises ashaft 49, suitably mounted on the top of the stove and extended This 10H mounted upon the side of the pipe, and having sectors and portstherethrough corresponding in of the stove, where it is provided with anoperating handle 50, in accordance with the previous disclosure. At itsinner end a cam as corresponding to that before described, is'fixed onthe shaft and engaged with the edge of the strip or for the operationpreviously described. 7

In Figures 7 and 8, the manner of embodying this invention upon a smokepipe as a check draft is illustrated, in this instance, a speciallyformed port plate M is suitably shaped to be front elevation to thoseshown in Figures 1 to d. is secured upon the smoke pipe t2. A shutter 53is mounted pivotally over the plates 58 by means of a shaft 56 extendiametrically across the smoke pipe and mounted revolubly thereinconventionally. This shaft is formed with a crank 55 centrally of thepipe, and suitably fixed on the exterior of the pipe in accordance withthe prior disclosure, there a a bimetallic strip 56, its point ofattachment being located a distance vertically irom'the" level of theshaft 56, and its swinging end being located closely adjacent the samelevel of the shaft 58, and connected to the crank E5 by means of a link51 extended slidably through a small aperture in the side of the pipe. Acan adjustment for the bi-metallic strip 56 is providedin a shaft 58,mounted revolubly in the pipe t2, one end extending through the. pipebeside the strip 56 and having a cam 39" thereon engaged with the stripas before described, the opposite end of the shaft being provided withthe operating hand lever sex which may be coordinated with an indexdevice as described in connection with Figures 1 to 4. If desired, aguard piece 59 may be incorporated with the bi-metallic strip 56,constructed in a form similar to thatofthe guard piece 3| before ment,size, and construction of parts, as well as substitution of equivalentsmay be carried out without departing from the spirit of theinvention,'as more particularly set forth in the appended claims.

I claim:

I. An automatic draft control for stoves and the like consisting of aflue member, a thermostatic bi-metallic strip fixed at one end inrelation thereto and having its opposite end free to swing undervariations of temperature, a port plate in the flue, a shutter movablethereon to close the port plate and to open the same, op-

erative connections between the swinging end 5 of said bi-metallic stripand said shutter, said strip extending beside said flue inspaced-relation, a shaft revolubly mounted across the flue, adjacent anintermediate .portion of the strip, substantially at right angles to thestrip, and having a spiral groove cam thereon, the groove receiving anedge portion of the lei-metallic strip, a pointer lever on the oppositeend of the shaft, and a channel guard device mounted between the flueand said bi-metallic strip, open at the top and bottom and having sideflanges provided with vertically spaced apertures.

2. In a stove, an automatic draft control therefor, consisting of astove body having a combustion chamber and a bottom air inlet thereto, a

'flue fixed in relation to the stove communicating at right angles fromthe strip 41, beyond the side 7 at its one endwith said draft inlet andextending upwardly therefrom, aport plate fixed across the flue, ashutter movable thereon toclose the port plate and open the same, abi-metallic strip arranged longitudinally of the fine, and secured infixed spaced relation thereto at a distance from the shutterand havingan end portion ar-' ranged to swing adjacent the shutter under-action ofheat variations, a link connection between the swinging end of thebi-metailic strip and said shutter, for operation of the latter byvariations of temperatures, said flue being mounted in close spacedrelation to the stove body, said strip being at the side of the fluenext adjacent the stove, a channel-shaped guard device on the flue artlyclosing the space between the flue and stove, whereby an air draft isformed adjacent the bi-metallic strip, a shaft revolubly mounted acrossthe hue substantially at right-angles to said strip and with one endextended through the flue beside the strip and spaced therefrom, aspiral cam screw device fixed on the shaft b'eside the strip andreceiving a strip edge in said groove, and the opposite end 01 the shafthavingv an operating handle thereon outwardly of the CLENNIE B HARREIL.

